Arthritis, more particularly osteoarthritis, is a degenerative joint disease commonly occurring in humans and in companion animals. See for example Richardson et al. (1997), Vet. Clin. North Amer. Small Animal Practice 27, 883-911.
Osteoarthritis involves progressive deterioration of articular cartilage, with loss of proteoglycan and collagen and proliferation of new bone, accompanied by a variable inflammatory response within the synovial membrane. It is the most common form of joint and musculoskeletal disease affecting dogs but is relatively uncommon in cats. See for example Schoenherr et al. (2000) in Hand et al., eds.: Small Animal Clinical Nutrition, 4th ed., 907-921, Walsworth Publishing Co., Marceline, Mo.; Hedborn et al. (2002) Cell Mol. Life Sci. 59, 45-53; Pool (1999) Front. Biosci. 4, D662-D670.
Management of osteoarthritis can include pharmacological treatments, surgery, nutraceutical administration and diet management. Such current management approaches have, however, focused on symptomatic relief and as such they have not been entirely successful in disease management or in treating the underlying pathologies. Hence there remains a continuing need for new approaches in managing osteoarthritis in companion animals, more particularly dogs.
Omega-3 (also known as n-3) fatty acids are needed in diets of mammals. They are naturally occurring materials in foods and have been used in dietary supplements. Schoenherr et al. (2000), supra, reviewed use of fatty acids including n-3 fatty acids in inflammatory disease including arthritis, and referenced a compilation by Miller et al. (1992) Canine Practice 17(6), 6-8, of observations of dog owners who perceived improvement in clinical signs of arthritis in their dogs when treated with fatty acids for dermatological problems.
Three omega-3 fatty acids are currently of most interest as dietary components: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and alpha-linolenic acid (ALA). Hitherto no great distinction has been drawn among these three.